Papr reduction in a microwave backhaul outdoor unit

ABSTRACT

Aspects of methods and systems for PAPR reduction in a microwave backhaul outdoor unit are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application claims benefit from and priority to Indian ApplicationNo. 1988/DEL/2015, filed Jul. 1, 2015, and U.S. Application No.62/203,454, filed Aug. 11, 2015. The above-identified applications arehereby incorporated by reference herein in their entirety.

BACKGROUND

Limitations and disadvantages of conventional approaches to microwavebackhaul will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

Systems and methods are provided for PAPR reduction in a microwavebackhaul outdoor unit, substantially as shown in and/or described inconnection with at least one of the figures, as set forth morecompletely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a diagram illustrating an example microwave backhaul outdoorunit (ODU).

FIG. 1B is a diagram illustrating an example microwave backhaul outdoorunit (ODU) configured to operate as a repeater.

FIG. 2A is a generalized block diagram of circuitry of the ODU of FIG.1A.

FIG. 2B is a generalized block diagram of circuitry of the ODU of FIG.1B.

FIG. 3 illustrates signal levels before and after PAPR reduction.

FIG. 4 is a flowchart illustrating configuration of the ODUs of FIGS. 1Aand 1B.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A is a diagram illustrating an example microwave backhaul systemcomprising an indoor unit (IDU) and an outdoor unit (ODU). The ODU 120 acomprises subassembly 114 a and antenna 116 (e.g., parabolic dishantenna) mounted to a structure 122 (a tower in the example shown). Inoperation, signals from IDU 150 are received by subassembly 114 a vialink 152 (e.g., coax, fiber, wireless, or any other suitable link) andprocessed for transmission onto a wireless microwave backhaul link viaantenna 116. The processing performed in subassembly 114 a is furtherdescribed below.

FIG. 1B is a diagram illustrating an example microwave backhaul outdoorunit (ODU) configured to operate as a repeater. The ODU 120 b comprisessubassembly 114 b and antennas 116 a and 116 b (e.g., parabolic dishantennas) mounted to a structure 122 (a tower in the example shown). Inoperation, the ODU 120 operates as a repeater such that a microwavesignal is received via antenna 116 a, processed by subassembly 114 b,and then transmitted via antenna 116 b. The processing performed insubassembly 114 b is further described below.

FIG. 2A is a generalized block diagram of circuitry of the ODU ofFIG. 1. The example implementation of circuitry 114 a comprisesanalog-to-digital converter (ADC) 204, channelizer 206, PAPR reductioncircuitry 208, digital-to-analog converter (DAC) 214, upconverter 210,and power amplifier 212.

The analog-to-digital converter (ADC) 204 concurrently digitizes theentire IF signal (thus, concurrently digitizing the entire range offrequencies allocated for communications from the IDU 150 to the ODU 120a on the link 152.)

The channelizer 206 selects one or more desired subbands of thedigitized L-band signal and conveys them to PAPR reduction circuit 208as signal 207.

The PAPR reduction circuitry 208 is operable to reduce thepeak-to-average-power ratio (PAPR) of signal 207, resulting in signal209. Referring briefly to FIG. 3, the PAPR reduction may operate tomaintain the peak level while increasing the root-mean-square (RMS)level of the signal to reduce the PAPR. The tradeoff for increasing theRMS level is a slightly higher noise floor for signal 209, but the RMSrises more than the noise floor.

Returning to FIG. 2A, DAC 214 converts the signal 209 to an analogrepresentation, the upconverter 210 upconverts the analog signal back tothe microwave band, and the power amplifier 212 amplifies theupconverted signal for transmission via antenna 116 b. In anotherimplementation, where the circuits 204, 206, 208, and 214 are capable ofhandling the RF frequency, this signal may already be at the microwavefrequency and the upconverter 210 may be absent.

FIG. 2B is a generalized block diagram of circuitry of the ODU of FIG.1A. The depicted subassembly 114 b is similar to the subassembly 114 aof FIG. 2A, but additionally comprises a downconverter 202.

The downconverter 202 receives a microwave signal (where “microwave” isused to cover frequencies anywhere from 300 MHz to 300 GHz) from theantenna 116 a and block downconverts it (i.e., downconverts the wholeband of frequencies allocated for use by microwave backhaul link) to anintermediate frequency (IF) signal. The IF signal may, for example, bean L-band signal centered around 1 to 2 GHz. In another exampleimplementation, rather than downconverting to IF, the downconverter 202may downconvert to baseband. In still another implementation, where thecircuits 204, 206, 208, and 214 are capable of handling radiofrequencies, then the downconverter 202 may be absent.

The analog-to-digital converter (ADC) 204 concurrently digitizes theentire IF signal from the downconverter 202 (thus, concurrentlydigitizing the entire range of frequencies allocated for use by themicrowave link.)

The channelizer 206 and PAPR reduction circuitry 208 operate asdescribed above.

In another example implementation, repeater functionality may beperformed at the packet level. That is, a received μw signal may bedemodulated to recover a packet carried therein, and then the packetremodulated and sent on a μw signal. In FIG. 1B, as an example, this maybe performed by circuitry of subassembly 114 b in FIG. 1B. As anotherexample, in FIG. 1A, this may be performed by a combination of one ormore subassemblies 114 a and one or more IDUs 150.

FIG. 4 is a flowchart illustrating configuration of the ODUs of FIGS. 1Aand 1B. The process begins block 402 in which a signal to be transmitted(e.g., a signal from IDU 150 in ODU 120 a or a signal from antenna 116Ain ODU 120 b) is received. In block 404, link conditions of the outputmicrowave link onto which the signal is to be transmitted aredetermined. In block 406, the PAPR reduction circuit 208 is configuredfor transmitting the signal based on the determined link conditions. Forexample, if the outbound link is noise limited at the receiver, then thePAPR reduction circuitry 208 may be enabled to reduce PAPR for thissignal, but if the link is limited by some other factor, then the PAPRreduction circuitry 208 may be disabled and/or bypassed for this signal.As another example, the signal PAPR reduction can be used to increasethe average (e.g., RMS average) Tx power of the ODU when conditions onthe μw link are such that, on the far end receiver, the Rxcarrier-to-noise ratio (CNR) is limited by the channel and not by thetransmitter CNR. In this case, the increased Tx RMS power and thereduced TX CNR resulting from operations of the PAPR reduction circuit208 still result in an increase in Rx CNR, as compared to without thePAPR reduction circuit 208. In this manner, PAPR reduction circuitry 408may be dynamically configured based on available link budget (e.g., onperiodic basis, on a per-transmission-burst basis, and/or the like). Inblock 408, the signal is transmitted on the output bound link. As anexample, determining the link conditions may comprise determiningcarrier to noise ratio and then the PAPR reduction based be controlledbased on a tradeoff between PAPR and CNR.

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. In other words, “xand/or y” means “one or both of x and y”. As another example, “x, y,and/or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means“one or more of x, y and z”. As utilized herein, the term “exemplary”means serving as a non-limiting example, instance, or illustration. Asutilized herein, the terms “e.g.,” and “for example” set off lists ofone or more non-limiting examples, instances, or illustrations. Asutilized herein, circuitry is “operable” to perform a function wheneverthe circuitry comprises the necessary hardware and code (if any isnecessary) to perform the function, regardless of whether performance ofthe function is disabled or not enabled (e.g., by a user-configurablesetting, factory trim, etc.).

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip. Some implementations may provide a non-transitorycomputer readable medium and/or storage medium, and/or a non-transitorymachine readable medium and/or storage medium, having stored thereon, atleast one code section executable by a computing system, thereby causingthe computing system to perform processes as described herein.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A wireless backhaul system, comprising: an antenna operativelycoupled to a subassembly, wherein: the subassembly is configured toreceive a first signal, the subassembly includes a first circuit and asecond circuit, the first circuit is configured to select one or moresubbands of the first signal and to send the one or more selectedsubbands of the received signal as a second signal to the secondcircuit, and the second circuit is configured to reduce apeak-to-average-power ratio (PAPR) of the second signal and to transmitthe reduced PAPR signal via the antenna. 2-20. (canceled)